Adding user access level into process login?

Question

Is there anyway that I'll be able to add user access level through this process code? I have my register code, which will allow normal user to register. I will set the admin only through PHPMyAdmin. How can I define admin user access level with this process page?

CODE: login_process.php

<?php
error_reporting(E_ALL);
ini_set("display_errors", 1);

include_once 'includes/db_connect.php';
include_once 'includes/functions.php';

sec_session_start(); // Our custom secure way of starting a PHP session.

if (isset($_POST['email'], $_POST['p'])) {
    $email = $_POST['email'];
    $password = $_POST['p']; // The hashed password.

    if (login($email, $password, $mysqli) == true) {
        // Login success 
        header('Location: ./protected_page.php');
    } else {
        // Login failed 
        header('Location: ./index.php?error=1');
    }
} 

else {
    // The correct POST variables were not sent to this page. 
    echo 'Invalid Request';
}
?>

Code: Login function

function login($email, $password, $mysqli) {
    // Using prepared statements means that SQL injection is not possible. 
    if ($stmt = $mysqli->prepare("SELECT id, username, password, salt 
        FROM members
       WHERE email = ?
        LIMIT 1")) {
        $stmt->bind_param('s', $email);  // Bind "$email" to parameter.
        $stmt->execute();    // Execute the prepared query.
        $stmt->store_result();

        // get variables from result.
        $stmt->bind_result($user_id, $username, $db_password, $salt);
        $stmt->fetch();

        // hash the password with the unique salt.
        $password = hash('sha512', $password . $salt);
        if ($stmt->num_rows == 1) {
            // If the user exists we check if the account is locked
            // from too many login attempts 

            if (checkbrute($user_id, $mysqli) == true) {
                // Account is locked 
                // Send an email to user saying their account is locked
                return false;
            } else {
                // Check if the password in the database matches
                // the password the user submitted.
                if ($db_password == $password) {
                    // Password is correct!
                    // Get the user-agent string of the user.
                    $user_browser = $_SERVER['HTTP_USER_AGENT'];
                    // XSS protection as we might print this value
                    $user_id = preg_replace("/[^0-9]+/", "", $user_id);
                    $_SESSION['user_id'] = $user_id;
                    // XSS protection as we might print this value
                    $username = preg_replace("/[^a-zA-Z0-9_\-]+/", 
                                                                "", 
                                                                $username);
                    $_SESSION['username'] = $username;
                    $_SESSION['login_string'] = hash('sha512', 
                              $password . $user_browser);
                    // Login successful.
                    return true;
                } else {
                    // Password is not correct
                    // We record this attempt in the database
                    $now = time();
                    $mysqli->query("INSERT INTO login_attempts(user_id, time)
                                    VALUES ('$user_id', '$now')");
                    return false;
                }
            }
        } else {
            // No user exists.
            return false;
        }
    }
}

Example Code:

    if (login($username="admin_username") {
            // Login admin success 
            header('Location: ./protected_page.php');
} else （login($email, $password, $mysqli) == true）{
            // Login success
            header('Location: ./user.php');
        }
} else {
            // Login failed 
            header('Location: ./index.php?error=1');
        }

Answer 1

Well, it depends on how you are storing the data in your database but if your user table has columns : user_name, password, user_type.

when you check if user_name and the password match on your login function you could do :

SELECT user_name, password, user_type FROM users WHERE user_name = '".$email."' AND password = '".$password"'";

Then you check the number of returned rows, if 0 is returned then the credentials don't match, you don't log the user in. If they match, then you can use the user_level to redirect where you want.

If you can post your login function I could explain you showing the changes to do into the code.

edit : adding fixed functions after he posted he login function.

Login validation :

    include_once 'includes/db_connect.php';
    include_once 'includes/functions.php';

    sec_session_start(); // Our custom secure way of starting a PHP session.

    if (isset($_POST['email'], $_POST['p'])) {
        $email = $_POST['email'];
        $password = $_POST['p']; // The hashed password.

        if (login($email, $password, $mysqli) == true) {
            // Login success
            //Redirecting to admin protected page for instance
            if( isset($_session['user_type']) and $_session['user_type'] == 'admin' )
                header('Location: ./protected_page.php');
            else {
                //redirect to normal logged user
                header('Location: ./normal_user_logged.php');

            }


        } else {
            // Login failed 
            header('Location: ./index.php?error=1');
        }
    } 

    else {
        // The correct POST variables were not sent to this page. 
        echo 'Invalid Request';
    }
?>

Login function :

    function login($email, $password, $mysqli) {
    // Using prepared statements means that SQL injection is not possible. 
    if ($stmt = $mysqli->prepare("SELECT id, username, password, salt, user_type 
        FROM members
       WHERE email = ?
        LIMIT 1")) {
        $stmt->bind_param('s', $email);  // Bind "$email" to parameter.
        $stmt->execute();    // Execute the prepared query.
        $stmt->store_result();

        // get variables from result.
        $stmt->bind_result($user_id, $username, $db_password, $salt, $user_type);
        $stmt->fetch();

        // hash the password with the unique salt.
        $password = hash('sha512', $password . $salt);
        if ($stmt->num_rows == 1) {
            // If the user exists we check if the account is locked
            // from too many login attempts 

            if (checkbrute($user_id, $mysqli) == true) {
                // Account is locked 
                // Send an email to user saying their account is locked
                return false;
            } else {
                // Check if the password in the database matches
                // the password the user submitted.
                if ($db_password == $password) {
                    // Password is correct!
                    // Get the user-agent string of the user.
                    $user_browser = $_SERVER['HTTP_USER_AGENT'];
                    // XSS protection as we might print this value
                    $user_id = preg_replace("/[^0-9]+/", "", $user_id);
                    $_SESSION['user_id'] = $user_id;
                    // XSS protection as we might print this value
                    $username = preg_replace("/[^a-zA-Z0-9_\-]+/", 
                                                                "", 
                                                                $username);
                    $_SESSION['username'] = $username;
                    $_SESSION['login_string'] = hash('sha512', 
                              $password . $user_browser);
                    // Login successful.
                    $_SESSION['user_type'] = $user_type;
                    return true;
                } else {
                    // Password is not correct
                    // We record this attempt in the database
                    $now = time();
                    $mysqli->query("INSERT INTO login_attempts(user_id, time)
                                    VALUES ('$user_id', '$now')");
                    return false;
                }
            }
        } else {
            // No user exists.
            return false;
        }
    }
}